Cathodic protection system and electrode holder



Oct. 27, 1959 H. s. PREISER 2,910,420

CATHODIC PROTECTION SYSTEM AND ELECTRODE HOLDER Filed July 51, 1957 3Sheets-Sheet l INVENTOR HERMAN S. PREISER ATTORNEYS H. S. PREISER Oct.27, 1959 CATHODIC PROTECTION SYSTEM AND ELECTRODE HOLDER Filed July 51;1957 3 Sheets-Sheet 2 INVENTOR HERMAN S. PREISER ATTORNEYS Oct. 27, 1959H. s. PREISER 2,910,420

CATHODIC PROTECTION SYSTEM AND ELECTRODE HOLDER Filed July 31, 1957 5Sheets-Sheet 3 I I l 2 36' 54 31 so 52 I 1 58 p 30'0 w, ,W NW so'b rINVENTOR HERMAN S. PREISER BY 21. 4., z mg/ ATTORNEYS Jnited States PatCATHODIC PROTECTION SYSTEM AND ELECTRODE HOLDER Herman S. Preiser, NorthSpringfield, Va. Application July 31, 1957, Serial No. 675,502

7 Claims. (31. 204- 196) (Granted under Title as, US. Code 1952 $66. 266

' vides a means for. determining the correct amount of protectivecurrent that will safely protect a ship from corrosion without damagingthe underwater paint coating.

Prior to. the instant invention, a conventional method ofdetermining-the amount of current necessary for protecting a ship fromcorrosion was by loosely trailing an electrode of silver-silver chlorideor copper-copper sulphate astern to the moving ship. The trailingelectrode method possesses a number of inherent disadvantages; the moreobjectional of which are:

0. Only average potentials of the ships hull, propeller and operatinganodes combined can be measured, which measurement is not a trueindication of the potential of the hull in a given area ofthe ship;

b. Trailing an electrode is cumbersome, often inconpropeller; and p c.Trailing electrodes generally are not sufficiently robustto use simpledirect reading voltmeters. Null reading potentiometers are required inorder that no. current is allowed to flow to or from the referenceelectrode element. V

Accordingly, a broad object of the present invention is to provide areference electrode wherein the above and other inherent disadvantagesof prior reference electrodes are eliminated.

Another object of this invention is toprovide ashockproof referenceelectrode for attachment to the hull of a ship. 7

Another object of this invention is to provide a reference electrodeincorporating a large but compact electrode element surface whichpermits measurements with simple rugged voltmeters.

Another object of this invention is to provide a reference electrodeincorporating a stuffing tube that permits easy, watertight electricalconnection to suitable meters within the ship.

Another object of this invention is to provide a reference electrodepossessing nonpolarizing characteristics under low currentdrainfor useas a sensing elementin an automatically controlled cathodic protectionsystem.

Another object ofthisinventionis. to provide areference. electrodeincorporating a. streamlined; housing with water passages therein; sodesigned as .tokeepa relatively stagnant poultice of electrolyte(seawater) in contact withthe electrode element;

venient and subject to damage and entanglement. by the 231M520Fatentedfict. 27, 1959 This invention, together with the above and otherob-. jects and advantages is set forth in more technical detail in thefollowing description and accompanying drawing in which like referencecharactersdesignate like parts throughout the several views and wherein:

Fig. 1 shows a schematic wiring diagram of a reference electrode hook-upfor an. impressed current cathodic protection system;

Fig. 2 is a transverse section illustrating a first embodiment of areference electrode'assernbly in accordance with this invention;

Fig. 3 is a top plan view of the reference electrode assembly shown inFig. 2;

Fig. 4 is a transverse section similar to Fig. 2, illustrating a secondembodiment of a reference electrode assembly in accordance with thisinvention; and

Fig. 5 is an elevational view, on a reduced scale, of the unitaryreference electrode assembly shown in-Fig. 4.

Referring now to the drawings, first to Fig. l, which illustrates animpressed current cathodic protection system applied to the hull 12 of asurface ship 10. The system includes a plurality of rectifier energizedanodes 14, each connected by a conductor to an. anode balancing control(not shown), which purpose isfor measuring current output of each anodeand'for' balancing differences in line resistance. For a completeillustration and detailed description of. the anode hook-up, referencemay he had to thecopending patent application of Herman S. Preiser etal., Serial No. 631,377, filed December 26, 1956, for Energized AnodeHolder Assembly.

Referring. still to Fig. l, in accordancewith this invention, fourreference: electrodes 16, to be referred to in detail hereinafter, aremounted on predetermined areas or stations. A, B, C and D onthe hull 12of the ship. Generally, the reference electrodes are located as-- faraway as practical from the anodes of the cathodic'prote'ction system.Inthe illustrated hook-up, cable leads 66, to be referred to indetailhereinafter,connect each of the several electrodes to terminals-A,B C and D,1respectively, of a selector switch 20. Each of the cableleads is brought into the hull through a stufiing tube, tobe referred toin detail hereinafter. A contact arm- 22 0f the selector switch isconnected by a cable 24'to the positive side of a suitable voltmeter.26, which voltmeter in the instant hook-up is a 20,000.0hm/vo1t meter.The nega tive side of the'voltmeter is grounded to the hull by a.

cable 28, thus completingthe circuit. r

In operation, by switching any one of the reference electrodes into thecircuit, an electrochemical cell is set up between therelectrode and thehull of'the ship. The voltage measured onthe meter 26 is the algebraicdifference between the half-cell potential of the silversilver chlorideof the sensing element of the reference electrode and the sea water, andthe half-cell potential of the hull steel and the sea water; the sensingelement or. electrode proper being exposed to the sea Water electrolyte,as described hereinafter. Now, when cur rent from an anode, such as 14,in the cathodic protectionsystem is impressed on the hull, the hullpolarizes orchanges its half-cell potental. The silver-silver chloridereference electrode, since it is not connected into the. hull circuit;except. through a veryhigh resistance 3. meter, 26, does not receive anyappreciable current from the anode, and, therefore, does not change itshalf-cell value. Therefore, any change in the reading of the meter 26 ofthe reference electrode circuit can be attributed to the change ofpotential of the hull. When the hull is polarized to a potential of--0.80 volts, referred to the silver-silver chloride electrode, it isconsidered protected from electrochemical corrosion. As pointed out inthe above patent application of Herman S. Preiser et al., Serial No.631,377, the current from the anodes to the hull may be regulatedmanually or automatically to bring the potential of the hull to thedesired value. As described in detail hereinafter, the construction ofeach of the reference electrodes is such that its half-cell value isstable and, constant and, therefore, it is used as an arbitraryreference standard for measuring the potential difference between it andanother metal, the hull steel, in a sea water electrolyte. Since thereference electrode value does not change, it can be assigned a zerovalue abritrarilyand therefore any reading on the meter 26 will actuallymeasure the half-cell value of the metal underconsideration; that is theselected area of the steel hull 12.

Referring now to Figs. 2 and 3 of the drawings, in this first specificembodiment of the invention the reference electrode assembly 16comprises a holder 30, an insulating disk 32, an insulating spacer 34, areference electrode or sensing element 36 and a stufiing tube 38. Thestuffing tube is welded, as by a ring weld 40, to the hull of the ship,and the holder is attached by machine screws 42 to a steel sole plate44, which sole plate is polyvinyl chloride, is formed with a recess orcavity 50 therein for reception of the electrode element 36, whichelement is cushioned within the cavity by fiber glass matting 52. Aplurality of openings 54 open into the cavity and a plurailty ofchannels 56 lead therefrom. The openings and channels that lead to andfrom the cavity in the holder are so designed that the sea waterelectrolyte surrounding the electrode element is rela tively stagnant,and together with the fiber glass matting, the sea water forms an eectrolyte poultice around the electrode element. The holder is formedwith suitably spaced openings for receiving the machine screws 42 andthese openings are conuterbored to receive the heads of such screws and,after attachment to the hull, the counterbores around the screw headsare filled with a dielectric, chemically resistant material, such as anepoxy thixotropic putty 58. The insulating disk 32 and insulating spaces34 are each formed of relatively rigid polyvinyl chloride sheet or othersuitable dielectric, chemically resistant plastic.

Referring 'still to Figs. 2 and 3, the electrode element 36 is formed ofa length of silver wire gauze folded back and forth upon itself inaccordion-like fashion with the corners trimmed to form a member that issubstantially circular in plan. One end of a silverwire the straightlength 60a (Fig. 3), is fused to one edge of the bottom .fold of theelectrode element leaving a loose length 60b of such wire free forattachment through a second silver wire to a cable 66, as describedhereinafter. After the gauze and lead wire are so assembled, theassembly is cleaned and dried. Then the element is dipped in molten(slightly above 455 C.) silver. chloride-A.S.C. and left in the solutionlong enough for the element to reach the temperature ofthesalt'andbecome wet. The silver chloride adhering to the elementis thenreduced to silver cathodically by using a platinum anode in a 3% GP.sodium chloride solution and a current of 200 milliamps for about onehour. After the electrode element is so prepared it is assembled in theholder, as described hereinafter.

The stufiing tube 38 comprises a steel, cup-shaped member 64 having acircular flange 64a on one end thereof and an opening 64b in the otherend. The flange 64a abuts the outer surface of the hull and ispermanently welded thereto by the ring weld 40. A two-wire cable 66 isinserted through the opening 64b in the bottom of the stufiing tube. Theouter end of cable 66 is stripped, exposing the't-wo copper wires 66awhich copper wires are twisted about a length of silver wire 68, asshown in Fig. 2, and permanently attached in good electrical contacttherewith by silver solder, leaving a free length 68a .(Fig. 3) of thesilver wire 68 for attachment to the length of silver wire 60]), asdescribed hereinafter. After the parallel copper wires 66a of cable 66have been secured to the inner end of the silver wire 68, the junctureis sealed in a molded rubber packing 70. Packing 70 is cylindrical inshape to conform to the bore of cup-shaped member 64, and the packing isformed with a reduced diameter portion for reception of a plasticpacking ring 72 and a glass-reinforced polyester resin gland nut 76. Abronze packing retainer 78 fits between the bottom of packing 70 and theinside bottom surface of member 64. v

In applying the electrode assembly to the hull of the ship, thecup-shaped member 64 of the stufling tube is inserted through ajsuitableopening in the hull until the flange 64a abuts the outer surface of thehull. Then the flange is welded to the hull, as by the ring weld 40.Simultaneously with the welding'of flange 64a, the sole plate 44 iswelded to the hull, first by' the ring weld 40, and then by the fairedweld 46. The outer end of cable 66 having previously been prepared asdescribed hereinbefore, the cable with the packing retainer 78 andmolded packing 70 applied thereto is inserted from outboard through theopening in the bottom of member 64 until the retainer abuts the member64 and packing 70 abuts the retainer. Then the packing ring 72 and glandnut 76 are applied to the stuffing tube and the gland nut is tightenedas necessary to expand the packing 70 into sealingcontact with the innercylindrical wall of member 64. Thus the cable is secured and sealed bythe stuffing tube and the outer end 68a of silver wire 68 is free forattachment to the silver wire 6% (Fig. 3)

of the electrode. The inner end of cable 66 is attached in suitablemanner (not shown) to its respective terminal in selector switch 20(Fig. 1).

The insulating spacer 34 is then located on the hull and the spacebetween the circular opening in the center of the spacer and the glandnut is filled with a dielectric, chemically resistant putty 79, such asa silicone rubber mastic. Then the insulating disk 32 with the free endof wire 68 projecting through a central opening therein is located onthe spacer 34. The free ends-of silver wires 60b 'and 68a are nowtwisted together, as shown at 69 in Fig. 3, and this juncture is heatedto a red heat and struck with a hammer thereby forming a good electricalconnection. The folded electrode 36 sandwiched in the fiber glassmatting is now placed in the cavity 50 of holder 30, with the silverwire 60 on the bottom side of the electrode element and slack wires 60band 68a coiled beneath the bottom fold of element 36 leaving slack inthe wire for future replacement. The holder with the packed electrodeelement now contained in the cavity 50 is secured to the sole plate bythe machine screws 42, after which the counterbores are filled with'theepoxy thixotropic putty 58, the outer surface of which putty isstreamlined to the contour of the holder.

Thus there is provided a streamlined, shockproof housing for attachmentto the hull of a ship or the like, and which housing contains anelectrode element made up of a large area of silver gauze with arelatively large amount of silver chloride fused and chemically reduc edon the silver constituting a robust cell capable measuring element.

of drawing fl of a milliampere, of current, continuously withoutappreciably affecting theaccuracy of the'silver This construction,permits the use of a 10,000 ohm/volt or higher resistant voltmeter formaking the hull potential readings andalso allows a sufficiently strongvoltage signal to be amplified in automatic control cathodic protectionsystems. The water passages in the housing or holder permit freeflooding of the electrode element but at the same time keeps arelatively stagnant poultice of electrolyte (sea water) in contact withthe electrode element. The stagnant sea water surrounding the silverelectrode element becomes saturated. with. silver ions andv thereforeproduces stable readings. because of the, achievement of electrochemicalequilibrium.

. Referring now.- to Figs. 4 and 5 of the drawings, which illustrates asecond. embodiment of the invention, and wherein-parts similar to thoseof the Figs. 2 and 3 embodiment are given like reference characters,primed. In the Figs. ,4. and. 5 embodiment the reference electrodeassembly/. 16 comprises a holder 30', a reference electrode or sensingelement 36' and a stufing tube 33. The. stufiing tube is welded by thering weld 40' to the hull 12 of the ship and the holder 30' is attachedby machine screws 42' to the sole plate 44, which sole plate is weldedtothe hull by the faired weld 46' and by the ring weld 40,. I H

The holder 30 of theiFigs. 4 and 5 embodiment is molded of dielectric,chemically resistant plastic, such as. rigid unplasticized polyvinylchloride, and it is made up-of two sections 30'-a and 30'b. Section 30'ais formed with a cavity 50 for reception of the electrode element 36,which element is cushioned in the cavity by fiber glass matting 52'. Aplurality of, openings 54 open into the cavity and a plurality ofchannels 56 lead therefrom. As in the Figs. 2 and 3 embodiment, theopenings 54 and channels 56 are so designed that the sea waterelectrolyte surrounding the electrode element is relatively stagnant.Section 30b of the holder is formed with an integral shank portion 30.cthatfits into the stuffing tube and is sealed therein by a pair of0.-rings 31. During assembly, as described hereinafter, sections 30'aand 30 b of the holderare cemented together at their abutting surfaces30d. v

The electrode element 36 of the Figs. 4 and 5 embodiment is formed offolded. silver wire gauze and the silver gauze is treated with silverchloride and electrolyzed as described hereinbefore with reference tothe electrode element 36. However, in the Figs. 4 and 5 embodiment, theelectrode element 36' includes a silver backing piece 37 and a silverprong or rod 39. The prong is permanently attached to the backing pieceby swaging under red heat and the backing piece is likewise attached tothebottom fold of element 36 by swaging under red heat.

The stuffing tube 38' of the Figs. 4 and 5 embodiment of the instantinvention is generally similarto the stutfing tube shown in Figs. 8 and9 of cop'ending patent application of Herman S. Preiser et al., SerialNo. 675,503, filed July 31, 1957, and currently identifed as Navy CaseNo. 23,911. The stufiing tube 38 comprises steel, tubular member 64'having a circular outer flange 6.4faand an inner flange 64b. Flange 64aabuts the outer surface of the hull and is weldedthereto by the ringweld 40. The inner flange 64b separates the tubular member into an innerand an outer bore, with the inner bore receiving a cable connector and apacking to be referredto. hereinafter, 'andthe outer bore receiving theshankj30'c of formed with-oppositely directed bores therein with theinner. bore receiving the stripped end; of the cable and the outer boredetachably receiving the electrode rod 39. As shown, the outer bore ofthe connector is much longer than the inner bore and this portion of theconnector is provided with longitudinal slots, not shown, which providea resilient fit with the. inner end of the electrode rod. A packing cone74', made of Teflon or similar dielectric, chemically resistantmaterial, fits within the inner bore of the stufling. tube, surroundstheelectrode rod and seals the openingin flange 64.77, A brass gland ring76 surrounds the cable and fits between the inner end. of packing member70 and the outer end of a gland nut 78, which gland nut isscrew-threaded into the inner end of the 'stufiing tube. For a detaileddescription, of the manner ofpreparing the cable, connector and moldedrubber packing, and of inserting and sealing this subassembly within thestufling tube reference maybe had to the above patent application ofHerman S. Preiser et al., Serial No. 675,503.

As pointed. out hereinbefore, the disconnect type of reference electrodeincorporated in the Figs. 4 and 5. embodiment of the invention permitsfactory fabrication of the parts under carefully controlled conditionsand the assembly (Fig. 5). is readily removed as a. unit from thestutfing tube for inspection and/or recalibration. That is, infabricating this reference electrode, the holder sections 30'a and. 3012are molded separately. The electrode element 36', with the backing plate37 and rod 39 attached thereto, is treated with silver chloride. Thetreated electrode element subassembly properly positioned in a suitablemold and section 30'b of the holder is. formed in a manner such that theshank portion, 3 0'0 is molded integrally around the electrode rod 39,leaving the folded electrode element free, which element iselectrolized, as described hereinbefore. The electrode element iswrapped or sandwiched with the-fiber glass cloth or matting 52 and thissubassembly is placed in the cavity 50' of holder section 30a. Thecomplementary surfaces of sections 30'a and 3tlb are coated with asuitable adhesive, and the two holder sections are pressed togetherforming a relatively permanent joint along the line 30'd. Thus, theelectrode assembly (Fig. 5) is completely fabricated at the factory andis ready for installation as a unit on the hull of a ship or the like.

Assuming that the stufling tube with the cable assembly located thereinis attached, to the hull, all that is necessary to completetheinstallation is. to insert the rod 39 of the electrode assembly intothe stufiing tube with the rod resiliently gripped by the connector 70and the shank Portion 30'c of the holder sealed in the-stufiing tube bythe O-rings 31. Then the machine screws 42 are threaded into the tappedholes in the sole'plate and the putty 58 applied to, the counterboresaround the screw heads. The gland nut 78 of the stuffing tube is thentightened from inside the hull and in so tightening the gland nut, therubber packing 72 is compressed against the cylindrical wall of thestuffing tube sealing the same. Tightening of the gland nut also causesthe slotted end of the connector to more firmly griputhe end. of theelectrode rod.

To remove the electrode assembly from the hull, all that is necessary isto remove the machine screws. 42 and loosen gland nut 78 whereupon theelectrode assembly may be removed from. the stufiing tube. As statedhereinbefore, the electrode assembly (Fig. 5) is fabricated and sealedat the factory and ordinarily'there is no need to open such, assembly.However, should it become necessary to, for example, inspect theelectrode element, access may be had thereto by prying the two sections3021 and 30'!) of the holder, which sections may again be cementedtogether after the inspection and/or repair is completed.

It is to be noted, in each of the illustrated embodiments of theinvention that the reference electrode assembly is relatively flat,streamlined and circular in plan. The assembly may however take otherstreamlined shapes. For example instead of circular in plan, theelectrode assembly may be elongated, semi-bullet shaped fairing, inwhich case, the electrode element may be formed as a concentricallywrapped cylinder of silver gauze, treated with silver chloride andelectrohzed.

Without further description, it is thought that the novel features andadvantages of the invention will be readily apparent to those skilled inthe art to which this invention appertains, and it will, of course, beunderstood that changes in form, proportions and minor details ofconstruction may be resorted to without departing from the spirit of theinvention and scope of the claims.

What is claimed is: i-

1'. A reference electrode assembly for use with a cathode protectionsystem for a metal structure wherein the metal structure is exposed toan electrolyte and forms the cathode of the system, said assemblycomprising an electrode element formed of electrochemically stablematerial, an inert, dielectricchemicallyresistant holder for theelectrode element, and means forattaching the holder to the metalstructure, said holder comprising a relatively flat, disk-like structurehaving a streamlined exterior surface and interior Walls forming acavity in the interior thereof for receiving the electrode element, aporous, dielectric, chemically inert matting encasing the electrodeelement within the cavity of the holder and spacing the electrodeelement from all of the said interior walls .forming such cavity saidholder being formed with fluid passages therein leading to, and from thecavity for flow of the electrolyte to the electrode element, saidelectrode element, said matting, said interior walls bounding the cavityand the fluid passages leading to and from the cavity being soconstructed and arranged as to cause the electrode element to besurrounded on all surfaces thereof by a relatively stagnant bath ofelectrolyte, and said electrode element having an electrical conductorconnected thereto and leading therefrom to the exterior of the holderfor connection to an electrical circuit.

2. A reference electrode assembly as set forthtin claim 1 wherein theelectrode element is formed of a plurality of layers of silver wiregauze folded back and forth one layer upon another forming a compactaccordion-like element.

3. A reference electrode assembly as set forth in claim 2 wherein thesilver wire gauze of the electrode element includes a coating ofelectrolized silver chloride, and wherein the relatively stagnant bathof electrolyte is'saturated with silver ions.

4. A reference electrode assembly as set forth in claim 1 wherein theelectrode element is formed of silver wire gauze having a silver backingplate attached thereto, and wherein the electrical conductor comprises asilver rod having one end thereof attached to the backing plate and theother end thereof extending through the holder for removable attachmentto the electrical circuit.

5. In combination, a reference electrode assembly for use with acathodic protection system for a metal structure, the metal of whichstructure forms the cathode of the system and which metalhas one surfacethereof exposed to sea water that forms the electrolyte of the system,means for removably attaching the electrode assembly to the exposedsurface of the structure and connecting means for electricallyconnecting the electrode assembly on the exposed side of the structureto an electrical circuit on an unexposed side of the structure, saidreference electrode assembly comprising an electrode element formed ofelectrochemically stable material, an inert, di' electric chemicallyresistant holder having a streamlined exterior surface and interiorwalls forming a cavity therein for receiving the electrode element, saidholder being formed with relatively small fluid passages from theexterior to the cavityforrestricted flow of sea water to and from thecavity, a porous, dielectric chemically inert matting encasing theelectrode elementwithin the cavity and spacing the electrode elementfrom all of the said interior Walls forming such cavity and in a manneras to submerge all surfaces of the electrode element in a relativelystagnant bath of electrolyte within the cavity, and said connectingmeans including aconductor connected to the electrode element, astuffing tube that penetrates the structure, a connector within thestufiing tube having one end thereof connected to the electric circuitand the other end thereof connected through the conductor to theelectrode element and means within the stuffing tube for sealing theelectrical connection.

6. The combination as set forth in claim 1 wherein the referenceelectrode assembly comprises a subassembly including the electrodeelement, the holder and the conductor constructed as a unit forremovable attachment to the exposed side of the metal structure with theelectrode conductor adapted for insertion into and removal from theconnector within the stuffing tube.

7. A reference electrode assembly for use with a cathodic protectionsystem for the metal hull structures of a ship exposed to sea waterelectrolyte and which metal forms the cathode of the protection system,said assembly comprising a relatively flat streamlined holder formedof adielectric material, chemically resistant to attack by seawater andcathodic reaction products formed on said hull from said protectionsystem, said holder having spaced interior walls thereof forming acavity for the reception of a reference electrode, said holder beingformed with a plurality of relatively small passages for restricted flowof sea water electrolyte to and from the cavity, means for attaching theholder to the exterior surface of the hull below the normal water linethereof, a silver-silver chloride electrode element located within thecavity of the holder and having the same general configuration as thatof the cavity of the holder, said electrode being formed of fine silverwire gauze having a coating of electrolyzed silver chloride-on allsurfaces thereof and constructed of a plurality of layers of such gauzefolded back and forth one layer upon another in a compact accordion-likestructure having a relatively large surface area compared to the area ofthe cavity, a matting of porous, dielectric chemically inert materialencasing the folded electrode element within the cavity and spacing suchelement from the said interior walls forming such cavity thereby forminga poultice of relatively stagnant sea water electrolyte about saidelectrode, and an electrical conductor having one end thereof connectedto the electrode element and an opposite end thereof adapted forconnection to an electrical circuit.

References Cited in the file ofthis patent UNITED STATES PATENTS Aaha-.1,

1. A REFERENCE ELECTRODE ASSEMBLY FOR USE WITH A CATHODE PROTECTIONSYSTEM FOR A METAL STRUCTURE WHEREIN THE METAL STRUCTURE IS EXPOSED TOAN ELECTROYLTE AND FORMS THE CATHODE OF THE SYSTEM, SAID ASSEMBLYCOMPRISING AN ELECTRODE ELEMENT FORMED OF ELECTROCHEMICALLY STABLEMATERIAL, AN INERT, DIELECTRIC CHEMICALLY RESISTANT HOLDER FOR THEELECTRODE ELEMENT, AND MEANS FOR ATTACHING THE HOLDER TO THE METALSTRUCTURE, SAID HOLDER COMPRISING A RELATIVELY FLAT, DISK-LIKE STRUCTUREHAVING A STREAMLINED EXTERIOR SURFACE AND INTERIOR WALLS FORMING ACAVITY IN THE INTERIOR THEREOF FOR RECEIVING THE ELECTRODE ELEMENT, APOROUS, DIELECTRC, CHEMICALLY INERT MATTING ENCASING THE ELECTRODEELEMENT WITHIN THE CAVITY OF THE HOLDER AND SPACING THE ELECTRODEELEMENT FROM ALL OF THE SAID INTERIOR WALLS FORMING SUCH CAVITY SAIDHOLDER BEING FORMED WITH FLUID PASSAGES THEREIN LEADING TO AND FROM THECAVITY FOR FLOW OF THE ELECTROLYTE TO THE ELECTRODE ELEMENT SAIDELECTRODE ELEMENT, SAID MATTING, SAID INTERIOR WALLS BOUNDING THE CAVITYAND THE FLUID PASSAGES LEADING TO AND FROM THE CAVITY BEING SOCONSTRUCTED AND ARRANGED AS TO CAUSE THE ELECTRODE ELEMENT TO BESURROUNDED ON ALL SURFACES THEREOF BY A RELATIVELY STAGNANT BATH OFELECTROLYTE, AND SAID ELECTRODE ELEMENT HAVING AN ELECTRICAL CONDUCTORCONNECTED THERETO AND LEADING THEREFROM TO THE EXTERIOR OF THE HOLDERFOR CONNECTION TO AN ELECTRICAL CIRCUIT.